In rubber products, particularly, a rubber composition to be employed in tires for cars, and the like, there are particularly required functional properties compared to a general rubber composition, and there is desired an increase of modulus in the rubber composition. And, in tires, particularly, a tire tread base composition and a tire-wire coat compound compared to other materials for parts, there is desired a large modulus.
In order to improve strength, etc. in a rubber composition employed for tires, etc., there are usually mixed a large amount of fillers such as carbon black, whereby, there is also a higher degree of stiffness in a rubber composition. For example, JP-A-07165996 Official Gazette proposes a polymer alloy in relation to a polyester resin/an epoxidized diene-based block copolymer/a rubber.
However, the polymer alloy proposed in the above-described Official Gazette unsatisfactorily has a disadvantage of poor compatibility between a polyester resin and a rubber because of a low molecular weight in the epoxidized diene-based block copolymer. Further, there becomes usually caused a high level of hysteresis by mixing with a large amount of carbon black in order to improve strength. Because of the high level of hysteresis, in the case that the polymer alloy is employed for tires, there is caused an excessive thermal accumulation, resulting in that there lowers a cut growth characteristics. Also, in the case that there is tried an improvement of a degree of cure in a rubber composition by mixing a large amount of sulphur, aging resistance is occasionally apt to lower. Still further, it is also unpractical to intend to attain a high level of strength by only the improvement of a degree of cure. That is, it is exceedingly difficult to obtain a rubber composition having a high level of properties such as strength required in tires for cars, etc.